Mechanisms behind reported in vivo anthelmintic effects of chicory (Cichorium intybus) in ruminants are poorly understood but it is likely that plant compounds, like sesquiterpene lactones (SL), play a role.
Objectives: The aim was to test the inhibitory activity of SL-containing extracts from two chicory cultivars on free-living and parasitic stages of Ostertagia ostertagi.
Methods: Leaves from chicory cv. Spadona and cv. Puna II were freeze-dried and SL extracted with methanol/water. Resulting extracts were incubated with cellulase enzyme and SL were purified from other plant compounds by normal solid-phase extraction. Purified extracts were dissolved in DMSO. O. ostertagi eggs from a mono-infected calf were hatched and first-stage larvae (L1) were used in a larval feeding inhibition assay (LFIA), while L3 cultured from faeces were used in a larval exsheathment inhibition assay (LEIA). O. ostertagi adult worms recovered post-mortem were used for motility inhibition assays (AMIA) and worm motility was evaluated after 6, 24 and 48 h of incubation (37oC). In all in vitro assays, decreasing concentrations of chicory extracts in PBS (1% DMSO) were tested in triplicates with 1% DMSO in PBS as negative control. Chemical profile of the extracts was analysed by liquid chromatography (LC).
Results: In the LFIA Spadona-extract inhibited larval feeding at significantly lower concentrations than Puna II-extract (EC50=31.5 [CI=25.9-38.3] g Spadona-extract/mL vs. EC50=121.1 [CI=95.2-153.8] g Puna II-extract/mL; p<0.0001). In the LEIA extracts from neither of the two cultivars interfered with the exsheathment of L3 at any of the tested concentrations. In the AMIA, Spadona-extract showed a significantly higher potency and exerted faster worm paralysis than Puna II-extract at all time points when tested at equal concentrations (p<0.0001). Preliminary LC analyses revealed different SL profiles of the extracts and further chemical characterization is undergoing.
Discussion: The observed anthelmintic effects of SL-containing extracts from chicory seem to be stage-specific as L1 and adult O. ostertagi but not L3 were affected. Different anthelmintic potency of SL-containing extracts from different chicory cultivars may help the identification of the most active(s) compound(s) and of cultivars with higher antiparasitic potential
